Page 3 - Lesson Notes-Ch.13 SA and Volumes(Cone)

Solved Examples

Example: 1
Find the curved surface area of a cone, if its slant height is 60 cm and the radius of its
base is 21 cm.

Solution:

It is given that:
Slant height of cone (l) = 60 cm

Radius of the base of the cone(r) = 21 cm

Curved Surface Area (C. S. A) = ?
22

=
=
C.S.A =  rl =  21 60 3960 cm
2
7
Therefore, the curved surface area of the right circular cone is 3960 cm 2 . .

Example: 2
2
The radius of a cone is 7 cm and area of curved surface is 176 cm . Find the slant
height.
Solution:

It is given that:

Radius of cone(r) = 7 cm
Curved Surface Area (C. S. A) = 176 cm
2
Slant Height of tent (l) =?

Now we know,
C.S.A = π r l

22
  7 l  = 176
7

176 7
 l = = 8cm

22 7
Therefore, the slant height of the cone is 8 cm.

Example: 3

The height of a cone 21 cm. Find the area of the base if the slant height is 28 cm.

Solution:

3